FRUIT WEIGHT IN PEACH: ASSESSING THE GENETIC POTENTIAL THROUGH PHENOTYPIC AND GENOMIC TOLLS

The trait fruit weight is of great agronomic importance for the commercial production of peach. In view of conducting a study of association mapping, the genetic diversity of peach accessions from the germplasm bank of MAS.PES was evaluated using amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSR). The results indicated that SSR markers were more informative and showed a high level of homozygosity in the accessions under evaluation. In studies meant for breeding of this species, the identification of quantitative trait loci (QTLs) explaining the phenotypic differences of this trait is important, because they can be used as a genomic tool in marker-assisted selection (MAS). In the present study, QTLs were detected through two approaches: 1. Linkage analysis, starting from a F2 population of 123 individuals from NJ Weeping (small fruit) x Bounty (large fruit), in which the software JoinMap was used to establish the relationship of linkage between the segregating markers, while the software MapQTL was employed to associate the data with the obtained phenotypic linkage map. 2. Association mapping, carried out on 70 peach accessions from the MAS.PES germplasm collection, in which the software Structure was used to analyse population structure: associations between markers and phenotypic traits were identified with the software TASSEL. As a result of linkage analysis, 877 single-nucleotide polymorphism (SNP) markers were grouped into 8 linkage groups and 34 QTLs related to fruit weight and size were identified. The results of the association analysis, performed using the General Linear Model (GLM), suggested the existence of 39 markers associated with fruit weight and size.